1. Field of the invention
The present invention relates to an electric power steering system and a method for verifying a steering angle thereof, and more particularly to an electric power steering system which calculates a final absolute steering angle when a difference between first and second absolute steering angles traced according to relative steering angles received from angle elements, respectively is within a reference difference, thereby improving a reliability of the final absolute steering angle, and a method for verifying a steering angle thereof.
2. Description of the Prior Art
As generally known in the art, a power steering system is applied to a vehicle as a means for mitigating a steering force of a steering wheel (handle) and securing a steering stability. As such power steering systems, existing hydraulic power steering (HPS) systems using a hydraulic pressure are widely used, but environment-friendly electric power steering (EPS) systems for helping steering of a driver by using a rotating force of a motor unlike the existing hydraulic method are being recently generally installed in the vehicle.
In such an electric power steering (EPS) system, an electronic control unit (ECU) drives a motor according to a travel condition of a vehicle detected by a speed sensor and a torque sensor to give a light and comfortable steering feeling during a low speed travel, give an excellent directional stability as well as a heavy steering feeling during a high speed travel, and allow a rapid steering in an emergency situation, thereby providing the driver with an optimum steering condition.
An electronic control unit of an electric power steering system according to the related art calculates a desired final absolute steering angle by using a first angle element for calculating an absolute steering angle, second and third angle elements for calculating relative steering angles, and a vernier algorithm.
However, since the electric power steering system according to the related art calculates a final absolute steering angle without verifying the relative steering angles received from the second and third angle elements, a reliability of the calculated final absolute steering angle is low. In particular, high reliability for an absolute steering angle is required as the ISO 26263 Standard is introduced.